MOSCOW - Last month's botched landing of a Russian capsule returning from the International Space Station was caused by the failure of an equipment module to separate from the capsule on time, a Russian space official said yesterday.

The Soyuz TMA-11 craft carrying U.S. astronaut Peggy Whitson, Russian cosmonaut Yuri Malenchenko, and South Korean bioengineer Yi So Yeon landed hundreds of miles off course when it bounced onto the steppes of northern Kazakhstan on April 11.

The three were subjected to severe G-forces, communications were disrupted, and Russian officials said the three had been in serious danger during the descent.

Alexei Krasnov, who heads Russia's cosmonaut space program, said that after the Soyuz separated from the space station, the equipment bay module was supposed to detach, allowing the capsule to enter the atmosphere and descend to Earth smoothly.

That did not happen, he said, and the Soyuz went into a "ballistic" descent.

He said Russian experts would soon finish the final report on the flawed landing, which was the second in a row and the third since 2003.

NASA officials have been watching the progress of the investigation closely, because Russian-built Soyuz and Progress ships are a primary way to get crew and cargo to and from the orbiting station.

Also, a Soyuz capsule is always docked at the station as an emergency "lifeboat" in case the crew needs it.

NASA officials on Monday set a May 31 launch date for the next space shuttle mission and said Russia's investigation into the Soyuz landing should not interfere.